Final answer:
The appropriate present tense form for the sentence "Mis amigos están enfermos hoy." is están.
Step-by-step explanation:
The appropriate present tense form for the sentence "Mis amigos están enfermos hoy." is están. This is because estar is used to express temporary states or conditions, such as being sick. In this case, the sentence is saying "My friends are sick today." The verb ser is used to express permanent characteristics or attributes.
Learn more about Spanish verb conjugation